The invention relates to active acoustic attenuation systems, and more particularly to a system for a correlated input acoustic wave, i.e. periodic, band-limited, or otherwise having some predictability.
The invention relates to the subject matter shown and described in commonly owned co-pending application Ser. No. 07/794,115, filed Nov. 15, 1991, and U.S. Pat. Nos. 4,677,676 and 4,677,677, incorporated herein by reference.
Active acoustic attenuation involves injecting a canceling acoustic wave to destructively interfere with and cancel an input acoustic wave. In an active acoustic attenuation system, the output acoustic wave is sensed with an error transducer, such as a microphone or an accelerometer, which supplies an error signal to an adaptive filter control model which in turn supplies a correction signal to a canceling output transducer, such as a loudspeaker or a shaker, which injects an acoustic wave to destructively interfere with the input acoustic wave and cancel same such that the output acoustic wave at the error transducer is zero or some other desired value.
The present invention provides an active acoustic attenuation system for attenuating correlated acoustic fields, including sound and vibration, and eliminates the need for an input transducer, such as an input microphone or an accelerometer sensing the input acoustic wave. Instead, the acoustic wave need only be sensed by the error transducer. The system has numerous applications, including attenuation of audible sound, and vibration control in structures or machines.